MOND GR: Bridging the Gap Between Newtonian and General Relativity?

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In summary, the MOND theory is in better agreement with experiment than Newtonian GR, but a bullet cluster poses a difficult problem for the model. There are other experimental counterexamples besides the Bullet cluster.
  • #1
quasar987
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I heard a general theory of relativity was constructed based on MOND rather than on Newton's law of gravitation. How well do the predictions of the MOND GR compare with the classical tests of GR (such as light bending)?

Basically, is it in better or worse agreement with experiment than Newtonian GR?
 
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  • #2
A related point is... can MOND adjust for the bullet cluster?
 
  • #4
Awesome ccdantas :!)
 
  • #5
MOND is not dead, but does appear injured. The bullet cluster does pose a difficult [albeit not insurmountable] problem for the model. The links provided by Christina provide a broad picture of current status.
 
  • #6
Are there other experimental counterexamples (falsations) besides the Bullet cluster?
 
  • #7
I am still inclined to believe that there must be something really profound behind the "empric" MOND factor a/(a^2 + a0^2)^1/2, especially taking into acount the "coincidence" that the best fit a0 (1.2*10-10 ms-2) is very close to c(lambda/3)^1/2

check :

"MOND as modified inertia" by Milgrom

http://arxiv.org/abs/astro-ph/0510117v1

really, really intriguing, don't you think so, another "numerical coincidence" ?
 
  • #8
It sounds suspiciously numerological to me chrisina, but, that is strictly my personal perspective - more hunch than reason. The standard model with 'dark' tweaks remains more attractive to me. Remember the atom - it's existence was postulated many centuries before is was cornered in a laboratory.
 
  • #9
I also prefer the "dark tweaks", (maybe I was influenced by Dark Vador too much when I was a kid... lol).
I am just very puzzled at how the curvature radius of a 4D de Sitter universe specified by the cosmological constant (3/lambda)^1/2 seems to play a very important role for the energy distribution profiles of the individual galaxies.
This requires an explanation.
 
  • #12
The situation seems to get more and more complicated and interesting. See here:

http://egregium.wordpress.com/2007/08/23/galaxies-and-dark-matter-apart/
 
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  • #14
jal said:
Does this fit in with weird and interesting.
from https://www.physicsforums.com/showthread.php?t=181546
"Gaping hole found in universe"
http://arxiv.org/abs/0704.0908

The MOND effect causes an increase in the gravitational strength at long distances. I suppose that an increase in the long distance gravitational strength could cause all matter to be concentrated in small regions. But I'm just guessing. This is way outside my realm of mediocrity.
 
  • #15
Garth is a very bright guy. He might be luring you into a serious discussion.
 

1. What is MOND GR and how does it differ from traditional general relativity?

MOND GR (Modified Newtonian Dynamics General Relativity) is a theory that attempts to explain the observed phenomenon of dark matter in the universe without the need for actual dark matter particles. In MOND GR, the traditional equations of general relativity are modified at low accelerations, such as those found in the outskirts of galaxies, to account for the observed dynamics without the need for dark matter.

2. How does MOND GR compare to observations of galaxy rotation curves?

MOND GR has been successful in predicting the observed flat rotation curves of galaxies, which is one of the main pieces of evidence for the existence of dark matter in traditional general relativity. However, it does not fully explain the observed behavior of galaxy clusters, which is a major challenge for the theory.

3. What are some other observational tests of MOND GR?

Aside from galaxy rotation curves, MOND GR has also been tested against observations of the cosmic microwave background, gravitational lensing, and the dynamics of galaxy clusters. While it has shown some success in these tests, there are still discrepancies and challenges that the theory must overcome.

4. Can MOND GR be reconciled with other theories of gravity, such as general relativity and quantum mechanics?

The compatibility of MOND GR with other theories of gravity is an active area of research. While MOND GR has been shown to be consistent with general relativity in certain regimes, there is still work to be done in understanding how it fits with other theories such as quantum mechanics.

5. How does MOND GR impact our understanding of the universe and cosmology?

If MOND GR is proven to be a valid theory, it would significantly alter our understanding of the universe and the role of dark matter in its structure and evolution. It would also have implications for cosmology and the study of the large-scale structure of the universe. However, more research and observational evidence is needed to fully integrate MOND GR into our current understanding of the universe.

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